Given:
There are given that the triangle ABC.
Where,

Step-by-step explanation:
According to the question:
We need to find the value for BC:
So,
To find the value of BC, we need to use the cosine rule:
From the cosine rule:

Then,
Put the all values into the given formula:

Then,
![\begin{gathered} BC^2=(4.5)^2+(3.3)^2-2(4.5)(3.3)cos100^{\operatorname{\circ}} \\ BC^2=20.25+10.89-29.7cos100^{\operatorname{\circ}} \\ BC^2=20.25+10.89-29.7(-0.17) \end{gathered}]()
Then,

Final answer:
Hence, the value of BC is 6.016 km.